Innate lymphoid cells type 2 and <scp>CD8</scp><sup>+</sup> T cells are perturbed in overweight and obese individuals with asthma
Authors: Sophia Björkander, Paul Maier, Maura Kere, Simon Kebede Merid, Lorenz Wirth, Whitney Wiegel, Sandra Ekström, Inger Kull, Anna Bergström, Erik Melén, Jenny Mjösberg, Christopher Andrew Tibbitt
Journal: Allergy (2023)

The prevalence of asthma and obesity is increasing globally and represents a major challenge. Obesity is associated with increased asthma risk and severity, an impaired treatment response and obese individuals with asthma present with a less defined type 2 response (1). Whereas innate lymphoid cells type 2 (ILC2) play a role in type 2-mediated asthma (2), their role in obese asthma remains unclear (3). In the present study, our aim was to address the frequency, phenotype, and activation status of ILCs and their T-cell counterparts, type 2 T helper (Th)2 and Tc2 cells, in normal weight and overweight/obese individuals with asthma and healthy controls. We assessed the ILC compartment alongside T cells in 87 individuals grouped as overweight/obese asthma (n = 20), normal weight asthma (n = 21), overweight/obese non-asthma (n = 25), and normal weight non-asthma (n = 21) (Data S2 [Ethical Permit: 2020–02922]; Tables SI and SII) (4). Peripheral blood mononuclear cells were analyzed for ILCs, CD4+, and CD8+ T cells using 18-parameter flow cytometry (Figure S1; Table SIII). To generate an unbiased overview of each compartment, we performed Phenograph analysis that identified 10 CD4+ Th cell clusters, 14 clusters of CD8+ T cells and ILCs, respectively (Figure S2A). Building upon this approach, principal component analysis (PCA) identified two groups (group 1–2) and an enrichment of Th2 cells in individuals with normal weight and asthma (Figure 1A,B; Figure S1). This was confirmed by conventional plotting and statistics (Figure 1C). In contrast, CD8+ T-cell separation was driven by expression of HLA-DR and IL-7Rα especially within the T cells re-expressing CD45RA (TEMRA) compartment in overweight/obese individuals (Figure 1A,B). These changes included increased expression of HLA-DR, CD56 and reduced expression of IL-7Rα in CD8+ TEMRAs of overweight/obese individuals with asthma (Figure 1D); a phenotype characteristic of innate-like TEMRA cells (5). Correlations between Body Mass Index (BMI) and/or percentage Body Fat (%BF) and CRTH2, HLA-DR and IL-7Rα expression on CD8+TEMRA cells were also observed (Figure S2B). Focusing on ILCs, the PCA contribution plots aligned more closely with PCA contribution plots of CD8+ T cells compared to CD4+ Th cells (Figure 1B). Further analysis of manually gated individual flow cytometer parameters revealed reduced frequencies of CD45RA+ ILC2s in overweight/obese individuals with asthma as compared to overweight/obese controls and a tendency for a reduction of these cells as compared to normal weight controls and individuals with asthma (Figure 1E). This was paralleled by an increased frequency of "inflammatory" CD45RO+ ILC2s (6) as compared to normal weight and overweight/obese controls which was not observed in normal weight individuals with asthma (Figure 1E). Moreover, we could observe an association between reduced CD45RA expression and higher BMI and %BF in the subset of CD117+ ILC2s in the overweight/obese individuals with asthma indicating a loss of naivety within the ILC2 compartment in this group (Figure 1F). Indeed, the CD117+ compartment expressed reduced levels of canonical ILC2 markers CRTH2, CD161, KLRG1, CD62L, and CD200R (Figure S3). For both CD117+ and CD117− ILC2 as well as naive ILCs, there was a significant correlation between IL-7Rα expression and BMI in the two overweight/obese groups (Figure 2A). In addition, IL-7Rα expression significantly correlated with %BF in CD117+/− ILC2 in overweight/obese individuals with asthma (Figure 2B). Given this, we evaluated the role for IL-7 and its receptor during the early stages of in vitro differentiation and activation of CD45RA+ ILC2 (Figure 2C). IL-7 increased the viability, cytokine production and expression of CD45RO as compared to ILC2 cultured with IL-33 alone (Figure 2D). Introduction of the steroid Dexamethasone (Dex) to cultures restored the expression of IL-7Rα, and IL-7 prevented Dex-induced cell death (Figure 2D). However, even in the presence of IL-7, ILC2s were still sensitive to Dex-induced reduction of cytokine production and CD45RO expression. The effects of IL-7 on surface markers were recapitulated by TSLP (Figure S4), sharing IL-7Rα usage with IL-7. Correlation analysis showed an association between the frequency of IL-7Rα+ ILC2 and CD45RO expression in the presence of Dex and IL-7 (Figure 2E). Herein, we observe that alterations in the CD8+ TEMRA cell and ILC2 compartments in overweight/obese individuals with asthma serve to immunologically distinguish them from normal weight individuals with asthma with IL-7 and its receptor constituting a potential fitness strategy for ILC2 in overweight/obese individuals with asthma. If and how ILC2 interact with the CD8+ T-cell compartment, especially within tissues such as the lungs in obese asthma, is an interesting area for future research, along with studies of larger groups of individuals with more defined asthma phenotypes and overweight/obesity. We thank the subjects and parents participating in the BAMSE cohort and all staff involved in the study through the years. We would also like to extent our thanks to the Flow cytometry team at CIM, MedH. The authors declare no conflict of interest. This study was supported by grants from the Swedish Research Council (2016–03086; 2018–02524; 2019–01060; 2020–02170), the Swedish Research Council for Health, Working Life and Welfare (2017–00526), Formas (2016–01646), the Swedish Heart-Lung Foundation, Center for Innovative Medicine (FoUI-976197), the European Research Council (TRIBAL, grant agreement 757,919), The Swedish Asthma and Allergy research foundation and Region Stockholm for cohort and database maintenance. Thermo Fisher Scientific kindly provided reagents for the allergen-specific IgE analyses. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 813343. Data S1. Data S2. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.